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Did you Know?

The grub stage of Japanese beetle can be a huge issue for highly maintained turf. Golf courses and athletic fields are often combating this pest as extensive damage can cause turf to loosen and tear up easily which affects their playability and overall function.

Japanese Beetles- Copper beetles eating holes in leaves

These beetles are visually attractive. However, both the larvae (grubs) and adults cause damage to plants. Grubs feed below ground on turf roots and organic matter below the surface, whereas adults chew.

Identification

Japanese beetles are about 1/2 inch in length and are oval shaped with copper wings and green heads. They are not graceful flyers, but can travel a long distance to find food or a mate. Leaves and flowers are covered in holes when adult beetles are active.

Clifford Sadof, Purdue University; Skeletonization of linden from Japanese beetle

Clifford Sadof, Purdue University; Skeletonization on chestnut from Japanese beetle

Dave Grieve; Adult Japanese beetle

Life Cycle

They overwinter as grubs below the turf and resume feeding subsurface for a couple months in the spring. Adults emerge around June and can be seen all the way into September. Adults dig small holes into the soil and lay clusters of eggs. This occurs throughout the lifetime of adults which lasts several weeks.

Damage

Adult Japanese beetles feed between the major veins of leaves. This results in a “skeletonized” appearance where leaf veins are left intact. Flowers are also fed on and appear somewhat shredded after extensive feeding. Lindens and cherries are commonly attacked trees, though Japanese beetle has an extensive host list exceeding 300 different plants.

Management

In low populations, plucking adults off plants and placing in soapy water is effective. However, this can be quite labor intensive in higher densities.

There are pesticides that can be applied to trees at specific times to protect them from beetle injury. These should always be applied after flowering to avoid contaminating flowers that may be visited by pollinators.

Over the past several years, there have been multiple types of lures developed that are designed to capture adult beetles in your yard. These lures are often baited with a mating pheromone and a floral attractant to draw in beetles. However, their effectiveness in regards to protecting your plants is questionable. It is not recommended to put these lures in your yard as they draw in outside beetles to your plants to feed before going to the lure to find a “mate.”